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bobba84
August 10th, 2014, 08:04 PM
... it has been in a wet shed for years. The motherboard has lots of green residue which I assume is corroded copper. (See images below)

It is complete but some parts are not original. The video card and MFM card seem to be newer, and it has a Seagate ST-238R in it.

May I please have some pointers on what is the best way to remove this?

Thank you!

19817
19818
19819

Bobby.

Chuck(G)
August 10th, 2014, 09:17 PM
It depends on how bad the corrosion is. Rather than wet it down with some water-based solution, as I might if it were due to a leaky battery, I'd probably start with some aerosol contact cleaner and a toothbrush. I use this stuff picked up at my local auto supply store:

http://www.eastwood.com/media/catalog/product/cache/1/image/412x/9df78eab33525d08d6e5fb8d27136e95/p39163.jpg

cr1901
August 11th, 2014, 02:28 AM
Would you mind documenting your journey on making this sad AT happy again? I'd be interested in seeing if you could restore it/put it to useful work :D.

snuci
August 11th, 2014, 04:36 AM
I've had worked on a motherboard in similar shape but it was an Apple Lisa. If you use a tooth brush, you could break off the teeth in the slots if they have been weakened by the corrosion so be very careful. I would soak this board in 1/2 vinegar and 1/2 water for 24 hours. You could very lightly brush it and see how you make out. If the teeth are weak and break, they would have broken when you inserted an interface card anyway but this will tell you if it is restorable.

bobba84
August 11th, 2014, 04:50 PM
Thanks guys! It's so good to have others with a common interest on here.

I will use this post to mark my progress - I want to restore it to it's former glory if at all possible.

Are you sure it's okay to immerse the whole board in the water/vinegar mix? Should I remove any IC's before doing this? Sorry... I just want to make sure.

I'm going to go to Jaycar today and get some electrical cleaner, I guess after it's had it's bath I'll spray that on and just be as gentle as I can.

I'll let you know how I go!

Bobby.

bobba84
August 11th, 2014, 05:11 PM
Also - here's a few more pictures :p

19825

19826

19827

19828

19829

snuci
August 11th, 2014, 05:18 PM
If you're comfortable taking out the socketed chips and knowing where they go back (draw a map and make sure you put them back right side up), I would remove them but also soak them as well. Where there was corrosion, the legs will also have corrosion on them. If the chip legs have weakened, you will lose some of them as you remove them. It really depends on the level of corrosion. In any case, you will have to see if it's worth replacing these. If a lot of chips have broken legs, it might be more economical to find a used/tested replacement motherboard.

In any case, it's worth a try to see how much damage is done. Good luck!

bettablue
August 11th, 2014, 07:05 PM
You are far more adventurous than I. I certainly wouldn't put much energy into this computer because of the corrosion and rust. But then again, if it was either really, really cheap, or free, then I guess you can't go wrong. I am in the market for a 5170 too, however, if I had gotten something that bad, I would be looking for a replacement mother board, video and hard disc controller. Then I would look underneath the mother board for any more signs of rust. I had one a few years ago that wasn't nearly as bad off as yours, but the corrosion WAS enough that connections in the card slots were easily broken. Some broke off just by gently rubbing my finger across them.

I wish you luck and good fortune and hope your time and energy aren't being wasted.

Chuck(G)
August 11th, 2014, 09:13 PM
Well, if I was determined to save this thing, the last thing I'd want to expose it to would be water. How do you intend to dry this thing thoroughly, especially with acetic acid reacting. At best, I'd make a 50-50 mixture of isopropanol and distilled water and rinse and dry it. Definitely not vinegar if the corrosion isn't due to a leaking battery--there's no point to it--you've got nothing to neutralize.

If you think toothbrushes are rough, you need a new dentist. The ones that I get from mine are very soft. Use a soft natural-bristle paint brush or an artist's sable brush if you're extremely paranoid.

Don't get your hopes up too high--you may find that some ICs have legs corroded right off. If the corrosion is from rodent urine, you're probably out of luck.

bobba84
August 11th, 2014, 09:28 PM
Thanks for the feedback guys.

I did get it cheap. So I don't have much to lose by trying. I don't have the finances to spend a lot on my hobby so I have to make do with what I can afford. It didn't have a battery in the case so I'll assume it's not from battery acid. I bought some isopropyl alcohol and some electronic cleaner today, I'll be very gentle with my toothbrush and see what happens. If something breaks, I'll look at replacing it if the rest of the board looks good enough to save after I've cleaned it.

Bobby.

orion24
August 11th, 2014, 10:44 PM
I'll be very surprised if you can get this thing running. It looks pretty bad. If nothing else works, I'd try the oven trick on this board. Maybe melting and re-solidifying the remaining soldering matterial would make the connections working, but it won't do anything about the copper corrosion.

cr1901
August 11th, 2014, 10:58 PM
I'd still give saving the thing a shot- these boards aren't going to get any more common (save for perhaps replicas).

Wouldn't the water and vinegar eventually fully evaporate anyway?

snuci
August 12th, 2014, 02:51 AM
Wouldn't the water and vinegar eventually fully evaporate anyway?

What I forgot to mention was the thorough rinsing afterwards. You have to flush it out with water (distilled preferred) to remove any traces of the water/vinegar mix. Vinegar is an acid which helps with corrosion but you don't want it left on to dry. While rinsing, I like to use a soft bristle paint brush to make sure any left-over corrosion or even caked on dust is removed. A tooth brush would work too. This gives the board a good cleaning. I also have a compressor that I use to blow out dust from new acquisitions but in this case I use that to blow out water that could be trapped under soldered chips or sockets/slots. Make sure the board is dry over a few days to make sure there is no water left.

On a side note, I have also tried putting a motherboard in the dishwasher with no soap but that didn't work as well for me. I still had to rinse and brush afterwards.

Whether it's worth it or not, it's a good exercise to try. After all, this hobby is a labor of love.

bettablue
August 12th, 2014, 02:58 AM
Mother boards can be found on E-Bay for very good prices from time to time. I would like to kick myself in the butt for selling the 5170 I had several years ago. Mine came with all of the vitals attached, even the back plate, and an IBM Model M keyboard. In my case though, I was just barely getting into vintage computing and didn't know what I had.

I wish you all the luck in the World getting your old beastie running again. As for me, well I'll just have to see if I can find one on the cheap, and hope it works. Then all I'll need to finish my IBM collection will be a 5155 Portable.

Again, good luck. Hope I've given you something to think about.

Cheers

~BB~




Thanks for the feedback guys.

I did get it cheap. So I don't have much to lose by trying. I don't have the finances to spend a lot on my hobby so I have to make do with what I can afford. It didn't have a battery in the case so I'll assume it's not from battery acid. I bought some isopropyl alcohol and some electronic cleaner today, I'll be very gentle with my toothbrush and see what happens. If something breaks, I'll look at replacing it if the rest of the board looks good enough to save after I've cleaned it.

Bobby.

mikey99
August 12th, 2014, 07:00 PM
Looking at your pictures ....I think that corrosion was caused by a leaking battery.
All the PC's I've seen with battery damage had that green/blue color corrosion.
When batteries leak they can produce a gas thats corrosive to surrounding components.
Someone may have removed the leaking battery years ago.

I've had good luck cleaning corrosion from boards with white vinegar and a soft toothbrush.
The vinegar neutralizes the electrolyte, which will prevent further corrosion.
And then rinsing with tap water afterwards.

Is there any similar corrosion inside the power supply ?

Chuck(G)
August 12th, 2014, 07:55 PM
Mikey, I think that corrosion is probably from moisture; could be from somewhere exposed to salt air. On the bottom, the position of the corrosion--and the green edge connector contacts say that to me.

At least that's the way I read it.

billdeg
August 12th, 2014, 08:02 PM
if this was a modern computer I'd just buy a new mobo and go from there. There are AT motherboards available, I'd be tempted to replace the motherboard. I have three or four AT motherboards (untested) on stand by should I get an AT that fails. You might want to just clean this one salvage what parts you think might be usable and wait for another AT to come along. My opinion....

[BTW - My Post # "2600" ]

bobba84
August 13th, 2014, 10:48 PM
Thanks guys.

I tried cleaning the corrosion with both electronic cleaner and isopropyl and neither would completely remove it. It took a lot of it off, but not all.

As it seems to be a no hope situation anyway I chucked the whole thing in a tub of soapy water with some isopropyl in to see what happens. I'll leave it for 24 hours, then leave it for a few days near a warm heater vent.

The power supply seemed fine inside. When I turned it on, the fan turned once then stopped. This repeated each time I turned it on. I vaguely remember these not working without a load attached? I didn't have time to investigate further than that.

Bobby.

geneb
August 14th, 2014, 07:51 AM
If it's not connected to the motherboard, it won't get a power good return and will turn off.

g.

Stone
August 14th, 2014, 08:19 AM
Plugging in a hard drive is normally sufficient to load the PSU.

geneb
August 14th, 2014, 08:25 AM
That's correct, but it won't handle the pwr_ok pin, which is required for the supply to start up.

g.

Stone
August 14th, 2014, 08:33 AM
Since the drive spins normally and continues to spin without a motherboard attached I don't believe you are correct. :-)

geneb
August 14th, 2014, 08:54 AM
The power good line may be restricted to the motherboard, but I doubt it. No where does he mention that the drive comes up without the board attached to the power supply.

g.

Stone
August 14th, 2014, 09:37 AM
No, I tried an AT PSU with only a drive attached (as I have done many times in the past) and it has always worked fine (as it did today). Just to be clear, without the drive attached, no PSU action.

Malc
August 14th, 2014, 11:17 AM
The Power good line is an output from the PSU to the motherboard, Like Stone said a good hard drive is usually sufficient to start the PSU.


That's correct, but it won't handle the pwr_ok pin, which is required for the supply to start up.

bobba84
August 14th, 2014, 08:28 PM
That was my understanding from other AT compatible PSU's too. But I've never come across one that required a load - but I've never had a real AT one either :)

The board came up quite clean after it's bath, there is still a little green on the edge connectors and on a few IC legs. It's looking pretty sad but I'll see what happens after it's spent a few days in the warm lounge.

Thanks as always for replies!

Bobby.

bobba84
August 15th, 2014, 03:59 AM
I tried the Power Supply with the HDD attached and it still worked for half a second then powered off. I'm not sure what to do now. The internal components all look fine. Does anyone know if there are common failure points on these? A google search didn't reveal much information about them.

Stone
August 15th, 2014, 04:21 AM
That's the ST-238R, right? If the drive doesn't spin and the PSU isn't staying on then it's likely the PSU is faulty. But first you need to confirm that the ST-238r spins on another PSU. If it doesn't you're back to square one. :-)

curtis
August 15th, 2014, 04:56 AM
Mentioned this to bobba in a pm, but for others, if the hard drive is bogged down and not spinning it can overload and shutdown the power supply.

Best bet is hooking up a floppy drive. Draws enough power to enable the power supply, but very rarely do they suck too much power.

Curtis

Stone
August 15th, 2014, 06:47 AM
Mentioned this to bobba in a pm, but for others, if the hard drive is bogged down and not spinning it can overload and shutdown the power supply.

Best bet is hooking up a floppy drive. Draws enough power to enable the power supply, but very rarely do they suck too much power.

CurtisBut floppy drives stay dormant until the BIOS is read. So plugging in a floppy drive by itself won't accomplish anything, will it? :-)

Malc
August 15th, 2014, 10:46 AM
A 5 1/4" floppy drive should put enough load on to start the PSU, I've used them before and it works

Stone
August 15th, 2014, 11:02 AM
A 5 1/4" floppy drive should put enough load on to start the PSU, I've used them before and it worksHow? Without a board it's not active? Have you even tried it as a stand-alone device with a PSU? A hard drive spins on powerup -- a floppy drive does not!

vwestlife
August 15th, 2014, 11:15 AM
FYI: IBM 5170s not equipped with a hard drive came with an electrical dummy load in its place, so if you don't have one hooked up (or a weenie modern HD that doesn't draw much current), you may need to construct a dummy load out of resistors or use an old hard drive to draw enough current to get the power supply to start.

Malc
August 15th, 2014, 11:30 AM
Have you tried it ?, Yes i have used a 5 1/4 floppy drive many times as a stand alone device to start a PSU, It just needs to be plugged in thus creating a load, It doesn't need to be active. When testing PSU's i do fully load them.


How? Without a board it's not active? Have you even tried it as a stand-alone device with a PSU? A hard drive spins on powerup -- a floppy drive does not!

Stone
August 15th, 2014, 12:47 PM
Have you tried it ?, Yes i have used a 5 1/4 floppy drive many times as a stand alone device to start a PSU, It just needs to be plugged in thus creating a load, It doesn't need to be active. When testing PSU's i do fully load them.How can that be? A floppy drive doesn't even light up without a controller card. It doesn't draw any current at that point. :-)

Have you tried it with a 5170 PSU? That's what I used.

Then I tried it with a 5160 PSU. Same as the 5170.

When I tried with a 286 clone PSU the PSU started without any load whatsoever.

You're aware that some at PSUs will start without anything plugged into them so, obviously, they don't count here. :-)

If you plug a floppy drive into a PSU that doesn't require an external load to start... well, I'm sure you see what I'm getting at. :-)

In any case, tell us exactly what you're using to get a PSU to start with *only* a floppy drive attached. I'm betting it's not a 5170 or 5160 PSU. And, since the OP is using a 5170 PSU my guess is his results in testing his PSU will require a hard drive and not a floppy drive to test it. Furthermore, I will state that an IDE drive will not suffice either in allowing a 5170 PSU to start up. It takes MFM, RLL, SCSI, or ESDI... only drives with electrical guts will suffice, IMO.

JDallas
August 15th, 2014, 01:24 PM
How can that be? A floppy drive doesn't even light up without a controller card.
***It doesn't draw any current at that point.***
It does draw current as soon as its available on the floppy-disk-drive's power cable-connector.

Notice that the floppy power cable-connector on a computer is always activated when the system is turned on. Power *is* drawn from the floppy power cable and energizes the floppy drive electronics. It just doesn't turn on the LED indicator because that can be controlled by the floppy data cable in most jumpered configurations.

The LED indicator responds to an open collector signal on the floppy data cable (34pin or 50pin ribbon cable). You could also turn on the LED indicator by jumpering a signal or two to ground, even without that floppy cable installed; i.e. no controller card connected.

If it drew no current,
and the floppy data cable was disconnected,
but you could jumper the drive's LED on by a shorting as signal or two to ground...

...that would be a magic act. :)

But its not magic, the first premise is false. It ***does*** draw current even without a controller connected.

Stone
August 15th, 2014, 02:25 PM
It ***does*** draw current even without a controller connected.But not enough to load a 5160 or 5170 PSU. Isn't that what we're discussing here?

Malc
August 15th, 2014, 02:33 PM
How can that be? A floppy drive doesn't even light up without a controller card. It doesn't draw any current at that point. :-)

The floppy drive draws current as soon as the PSU is switched on, the drive electronics are initialized .


Have you tried it with a 5170 PSU? That's what I used.

Yes


Then I tried it with a 5160 PSU. Same as the 5170.

I can't lay my hands on one right now.


When I tried with a 286 clone PSU the PSU started without any load whatsoever.

Yes i have those as well, The load is internal.


You're aware that some at PSUs will start without anything plugged into them so, obviously, they don't count here. :-)

If you plug a floppy drive into a PSU that doesn't require an external load to start... well, I'm sure you see what I'm getting at. :-)

Obviously


In any case, tell us exactly what you're using to get a PSU to start with *only* a floppy drive attached. I'm betting it's not a 5170 or 5160 PSU. And, since the OP is using a 5170 PSU my guess is his results in testing his PSU will require a hard drive and not a floppy drive to test it. Furthermore, I will state that an IDE drive will not suffice either in allowing a 5170 PSU to start up. It takes MFM, RLL, SCSI, or ESDI... only drives with electrical guts will suffice, IMO

An IBM AT 5170 PSU and no it does not start with no drive plugged in, I have used a Tandon FH TM-100-2A and a HH Matsushita and IDE hard drives all individually of course and the PSU starts successfully.

Stone
August 15th, 2014, 03:06 PM
Maybe it's because I'm using newer, HH floppies -- Teac drives, 55BV and 55GFR. But I've tried 240MB to 2.1 GB IDE drives and none of them will start the PSUs. The fan twitches quickly but that's about it.

Maybe the older floppies are loaded like the clone PSU is. I have no idea why there is this inconsistency. And then there is the IDE. I've even tried a really old TEAC 40MB drive and even it won't start the PSUs.

modem7
August 15th, 2014, 04:12 PM
Different make/models of switch-mode power supplies have different start-up loading requirements. It comes down to how they are engineered (the components used, configuration, etc.)

Some require no start-up loading at all.

For others, the start-up loading requirement varies considerably. For example, the Tandon full height floppy drive is enough of a load for the IBM 63W power supply. The start-up loading for the power supply in the IBM 5155 is commented on at [here (http://www.minuszerodegrees.net/5155/psu/5155_psu.htm)].

modem7
August 15th, 2014, 04:44 PM
I tried the Power Supply with the HDD attached and it still worked for half a second then powered off.
So either:
* Faulty power supply; or
* HDD not sufficiently loading the power supply; or
* HDD faulty in such a way that it overloads the power supply.

I have just now reconfigured my 5170 so that the power supply only powers the motherboard. The motherboard has no optional maths coprocessor (a 'power hungry' device), and no cards plugged into it. On three attempts (5 minutes between each attempt), the power supply started and ran.

I had no dummy load on the +12V line (specified by IBM for the 5170 power supply if no HDD), but maybe that is required for RELIABLE power supply start-up. Hard to tell. It may have only been a requirement for early versions of the 5170 power supply. Who knows?

In any case, what happens if you power up the power supply with only the motherboard connected (assumption: motherboard completely dried). Does the power supply run?

Stone
August 15th, 2014, 04:53 PM
So either:
* Faulty power supply; or
* HDD not sufficiently loading the power supply; or
* HDD faulty in such a way that it overloads the power supply.I would discount #2 since the drive in use here has no problem loading my choosy 5170 PSU. That leaves #1 and #3 as the most likely culprits. And I've already suggested that he determine which of those two it actually is:

http://www.vintage-computer.com/vcforum/showthread.php?43880-I-obtained-a-very-sad-5170&p=335690#post335690

paul
August 15th, 2014, 05:32 PM
... but maybe that is required for RELIABLE power supply start-up. Hard to tell. It may have only been a requirement for early versions of the 5170 power supply. Who knows?
No doubt the reason for the 5 ohm dummy load is to ensure the voltage regulation is optimal, not for startup. It seems to have been issue for early switchers while newer designs are not as fussy. Found the info on your site :) in the 5170 technical reference guide, section 3-4.
Years ago at work we purchased quantities of diskless 5170 units for use in our industrial control systems. Those of course had the dummy load but we chucked out everything except the motherboard and floppy drive. :(

modem7
August 15th, 2014, 05:38 PM
I would discount #2 since the drive in use here has no problem loading my choosy 5170 PSU. That leaves #1 and #3 as the most likely culprits. And I've already suggested that he determine which of those two it actually is:
http://www.vintage-computer.com/vcforum/showthread.php?43880-I-obtained-a-very-sad-5170&p=335690#post335690
"But first you need to confirm that the ST-238r spins on another PSU. If it doesn't you're back to square one."

Although, if the ST-238R doesn't spin on a different PSU:
1. The ST-238R is bad in a way that overloads the PSU; or
2. The ST-238R is good, but the OP unknowingly chose a PSU on which an ST-238R alone is not a sufficient start-up load.

Stone
August 15th, 2014, 05:48 PM
"But first you need to confirm that the ST-238r spins on another PSU. If it doesn't you're back to square one."

Although, if the ST-238R doesn't spin on a different PSU:
1. The ST-238R is bad in a way that overloads the PSU; or
2. The ST-238R is good, but the OP unknowingly chose a PSU on which an ST-238R alone is not a sufficient start-up load.1. Not necessarily. The ST238R could be unable to spin for any number of reasons only one of which is an overload.

2. I don't think that there is a PSU that this drive will not create a sufficient load for. It's an ST-225 and they're power hungry beasts. :-)

modem7
August 15th, 2014, 05:48 PM
No doubt the reason for the 5 ohm dummy load is to ensure the voltage regulation is optimal, not for startup. It seems to have been issue for early switchers while newer designs are not as fussy. Found the info on your site :) in the 5170 technical reference guide, section 3-4. (
Yes, the requirement for the dummy load is in the technical reference. That's why I earlier wrote, "specified by IBM for the 5170 power supply if no HDD".

modem7
August 15th, 2014, 06:04 PM
1. Not necessarily. The ST238R could be unable to spin for any number of reasons only one of which is an overload.
True. But if I change my earlier post to the following, there are still both 'good drive' and 'bad drive' possibilities.

Although, if the ST-238R doesn't spin on a different PSU:
1. The ST-238R is bad in a way that overloads the PSU; or
2. The ST-238R is bad in a way that results in the platters not spinning.
3. The ST-238R is good, but the OP unknowingly chose a PSU on which an ST-238R alone is not a sufficient start-up load.


I don't think that there is a PSU that this drive will not create a sufficient load for.
I think the IBM 5155 PSU (http://www.minuszerodegrees.net/5155/psu/5155_psu.htm) is a good candidate. I will see if I have an ST235R in my collection (packed away) to try it out. If I do have one, I will also try it out on my 5170 PSU.

Stone
August 15th, 2014, 06:13 PM
While you're at it, can you see if that 5170 PSU will start with only a floppy attached and if so which floppy(s) allow it to start and which don't. I can't get mine going with any but Malc can and it's still confusing as to why.

modem7
August 15th, 2014, 08:12 PM
I'm still looking for an ST238R.


While you're at it, can you see if that 5170 PSU will start with only a floppy attached and if so which floppy(s) allow it to start and which don't. I can't get mine going with any but Malc can and it's still confusing as to why.
SOME RESULTS FROM MY 5170

Loaded by motherboard: +5V line at 5.2, +12V line at 11.9
No load: Fan turns (slowly). +5V line at 8, +12V line at 4.3 (No, I have not accidentally reversed the figures.)

Some half-height 5.25" floppy drives:

YD-380: PSU fan turns. +5V line at 6.5, 12V line at 8.3
YD-580: PSU fan turns. +5V line at 7, +12V line at 7.1
JU-475-4: PSU fan turns. +5V line at 6.1, +12V line at 9.5
FR-506: PSU fan turns. +5V line at 7, +12V line at 7.1
SA455: PSU fan turns. +5V line at 5.5, +12V line at 11
FD-55G: PSU fan turns. +5V line at 6.5, +12V line at 8.2

Some half-height 5.25" hard drives:

ST-252-1: PSU fan turns. +5V line at 6.1, 12V line at 9.5
D5146H: PSU fan turns. +5V line at 6, 12V line at 10
3650: PSU fan turns. +5V line at 6, 12V line at 9.8
ST-225: PSU fan turns. +5V line at 5.2, 12V line at 11.9 <--- adequate load
ST-225N: PSU fan turns. +5V line at 5.2, 12V line at 11.9 <--- adequate load

So unlike a lot of switch mode power supplies for PCs, the 5170 power supply is not in the category of 'either it starts and runs, or not'.

There will be a tendancy for people to think that their 5170 power supply is running (to spec) based only on the fact that the fan is turning.

modem7
August 15th, 2014, 08:43 PM
I don't think that there is a PSU that this drive will not create a sufficient load for. It's an ST-225 and they're power hungry beasts. :-)

I think the IBM 5155 PSU (http://www.minuszerodegrees.net/5155/psu/5155_psu.htm) is a good candidate. I will see if I have an ST235R in my collection (packed away) to try it out.
I still have not found an ST238R, but I did find my spare IBM 5155 PSU. It is of the type where if inadequately loaded, the fan starts turning and there is some initial output voltage, but then the PSU quickly stops (fan stops and output voltages slowly drop to zero).

Although I earlier found the ST-225 to be an adequate load for my 5170's PSU, it is not an adequate load for my 5155 PSU. Two ST-225s were required for the 5155 PSU.

Stone
August 16th, 2014, 09:31 AM
Wow m7, that's a bunch of information. I see quite a bit of work there. Thanks for the insight and the valuable stats.

bobba84
August 17th, 2014, 01:03 AM
Hi guys!

I had a busy weekend so only tonight got to play with the 5170 again.

It seems in my case at least the ST-238R is not enough to power up the PSU by itself. Bear in mind though that it had spent more than ten years in someone's shed and might have bad tolerances on certain components inside it. I gingerly connected the motherboard to the PSU after a few days above a ducted heating vent, and flicked the switch. The PSU promptly powered up.

I then turned it off again and plugged the HDD in as well, and both it and the power supply made good sounding noises. The HDD heads did their self test, which to me sounded normal, a ticking followed by two quick sweeps of the platters then stayed dormant. The bearings sound quiet too, so I'm hoping I have an at least relatively healthy drive on my hands.

The motherboard, while far cleaner than it was, unfortunately has some bad corrosion around a few IC's near the keyboard port, as well and some stubborn corrosion on the ISA slots. I have yet to test it's functionality but I am not holding my breath.

As always, thanks so much for the responses and advice. I will post more pictures tomorrow after work. This rusty grandpa of a machine may yet see the light of day, so to speak.

Cheers!
Bobby.

cr1901
August 17th, 2014, 08:15 AM
Well, at least this is a sign that the corrosion didn't create any shorts...

k2x4b524[
August 17th, 2014, 11:53 AM
agreed, no shorts is good, Hopefully you can get that 5170 back into some sort of running order :)

bobba84
August 18th, 2014, 02:00 AM
So I played around a bit more tonight, I put in my POST card and powered the motherboard on. All the lights showing the voltages came on, but nothing came up initially on the two 7-segment displays. After a while one of them said either P or d (I'm not sure which way up it goes!) a few times, but that's it. I'm thinking this is maybe unintentional due to the inoperable state of the motherboard.

I removed the only socketed chip in the affected area (an intel chip labeled 8742) and found that the socket was badly corroded and a few of the contacts had broken, so I removed the socket and soldered the chip directly to the board. When I powered it up, nothing had changed.

I then noticed a missing component! I have no idea what was there before or what is does - it is labeled Y3 and is near the keyboard port. Does anyone know a) what it is (specs would be great as I can try to obtain a replacement and b) whether it is essential to basic operation?

I have attached pictures to show my progress visually.

If this does not fix the motherboard I think I am at the end of my abilities to diagnose it, unless anyone has another suggestion?

EDIT!!: Sorry, I forgot two bits of info. I checked the PSU output and all seems really good, including the power good signal. Also, the CPU gets warm after about 30 seconds, not too hot, about what I would expect.

Thanks to all!
Bobby.

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19942

modem7
August 18th, 2014, 04:16 AM
I then noticed a missing component! I have no idea what was there before or what is does - it is labeled Y3 and is near the keyboard port. Does anyone know a) what it is (specs would be great as I can try to obtain a replacement and b) whether it is essential to basic operation?
Y3 is a 32.768 kHz crystal that is part of the oscilator circuit (MC14069/Y3/C83/R27) that 'ticks' the RTC/CMOS chip (MC146818).
Diagram [here (http://www.minuszerodegrees.net/images2/5170_battery_circuitry.jpg)].

One POST code list for the IBM AT is [here (http://www.bioscentral.com/postcodes/ibmbios.htm)]. POST interaction with the RTC/CMOS chip doesn't happen until code 16. So if a missing Y3 is the only problem with the motherboard, I would expect a POST card to be showing, at the minimum, codes up to 16.

cr1901
August 18th, 2014, 04:51 AM
The 8742 is an 8042 variant, and should be the keyboard controller... The POST card should be read as "d", not "P". According to modem7's link, post code 0x0D is "keyboard controller reset," which is consistent with the chip that you soldered onto the board.

Perhaps the chip itself is bad, or needs more "persuasion" before it'll start working :P?

One thing that bothers me is that there's nothing written to the POST card port until 0x0d... I'd expect the POST card would have the number incremented in order...

bettablue
August 18th, 2014, 06:53 AM
Good morning Bobby my friend.

It looks to me that there is still an awful lot of that green corrosion on the bare metal of the components you've pictured. Are you sure you got it all out of the ISA sockets?

As far as what is at the A3 position, I don't know at this time since I don't have a 5170 board to look at.

You know... I keep wondering about the other components in the computer as well. Since there was that much corrosion on the mobo, what is coating the insides of the floppy. You also mentioned that you had tested the power supply and hard disc for operation, but again, I have to wonder how much of that green stuff is inside the drives. It seems to have gone everywhere. Hmm.

nige the hippy
August 18th, 2014, 01:52 PM
Looking at earlier pictures, I'd say you'd be incredibly lucky to get that motherboard going. The problem with water is that it likes to creep into tight spaces, many of those tight spaces being the various plated-through holes & Vias on the PCB. They look terrible, and plating-through is a bit dodgy at the best of times.
By all means have a go at resurrecting it, but don't beat yourself up if you can't.
Just a thought, you can always clean the resist layer off the really corroded areas with a "fibreglass pencil", you can meter them through top-bottom & solder a wire top & bottom if it's o/c. If the board's going in the bin, nothing to lose but time!

bobba84
August 18th, 2014, 02:19 PM
Thanks for the replies guys. Yes, it seemed strange to me that it went straight to 'd' on the post card - not even '0d'.

I'm getting the feeling that this board is a no hoper. I don't have the experience or the time to continue diagnosing it. I've been offered another board which I might take.

As for the other components, they are in remarkably good shape! The green corrosion seems to have started where the CMOS battery once was, and spread along the motherboard. The front half of the board is really fine, so my guess is at least some of the RAM chips and some other components might be useful to someone.

I have checked inside the power supply closely and there seems to be no hint of corrosion. Same with the other parts. I was surprised too, Thomas! I thought this plague would have spread to everything! So it seems the motherboard is the only bad part of this machine, apart from the two non-original ISA cards which had green edge connectors, and apart from the cosmetic condition of the case.

I will offer this board to the person who is offering me the replacement first, but if he doesn't want it, then I'd like to donate it to anyone who wants it, or could use the parts/components. If there are no takers, I'll keep it for parts.

Thanks a lot for all the wisdom and advice. I'll keep posting in this thread once the replacement board arrives!

mikey99
August 21st, 2014, 06:07 PM
I still think this is damage from a leaking battery. :D I've seen the ISA slot connectors covered with green residue just like that.
If you can get the board working, I would try cleaning up more of that residue with white vinegar and a toothbrush.

bobba84
September 9th, 2014, 03:06 PM
Update guys! My replacement motherboard should be on it's way very soon! I've cleaned and repainted the case (not the cover yet) and found a replacement video card and RLL controller, as the contacts were green and any attempt to remove the corrosion wore through the contacts. A few people have now said it was the battery leaking that caused this - that makes sense as the damage is centered around where the CMOS battery once was.

Thanks to all for your help so far - and I'll keep you posted with pics and news :)

mikamiko
September 10th, 2014, 10:07 AM
I never heard of such a thing can be cleaned using a rubber pencil eraser. many computer technicians who use it the way it is
http://amburadul101.tk/8/o.png

bobba84
October 1st, 2014, 02:25 PM
Hi guys,

Just an update - I finally had the time to have a look at the 5170 again. I got the replacement motherboard, connected it up to the power supply - and it won't boot! It is showing the same '6' by itself on the POST card as the other (corroded) board!

I've tried a minimal config with just the speaker, and with just the speaker and one of a few different video cards - nothing :(

Is it at all possible for a power supply to be 'bad' while providing all the right voltages??? I am at a loss to explain what is going on!!!

Are the 5170 power supplies the same as the later AT ones that 486's use? If so I could try starting it from that?

Any help would be very much appreciated.

Bobby.

Stone
October 1st, 2014, 02:32 PM
If the power supply has the standard P8 & P9 connectors it will work. You can even use an ATX power supply but you'll need the corresponding cable adapter to match the AT motherboard.

bobba84
October 26th, 2014, 01:38 PM
Hi guys,

Time for an update!! :)

I couldn't get to the 5170 for a few weeks as I had a heavy workload and my wife wasn't well (she's better now)... but after having a fresh look at everything I tried the new 5170 board on another power supply - and it worked!! :)

I then realised there was severe corrosion in the P8 and P9 connectors of the power supply! I really should have thought of this earlier. But anyway, I cut the connectors off a much newer, but dead, AT-style power supply and soldered them onto the cables of my 5170 supply. Now I have a working 5170! :D :D :D

I also went back to the guy that I bought it off and he had since found the original MFM/floppy controller and a full length, non-genuine EGA card in great condition. It seems they were stored much better than the 5170.

I have resprayed the case (using a colour that is close to, but not an exact match of the original) and am 95% putting it back together.

Please find below some pictures of my progress... and thanks again to everyone that helped me along the way!

Bobby.

21184
Bad power supply connector - notice the first two pins have snapped off! When tested with a multimeter from the top, it shows up okay.

21185
New connector soldered in, before being insulated

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AT case cover, being resprayed

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Another shot of the case, notice the colour difference.

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The AT, so far! :)

Caluser2000
October 26th, 2014, 01:49 PM
Good work.

billdeg
October 26th, 2014, 01:54 PM
here's to sticking with it.

bobba84
October 28th, 2014, 03:02 AM
So... It seems I spoke too soon.

The machine starts to do POST, but 75% of the time it freezes before finishing!

On the odd occasion it finishes post, at the point where it would boot from floppy, i get the error:
PARITY CHECK 1
00000 (S)

This tells me bank 0 is bad, although I don't know what the S is for.

Here's the problem - I've changed bank 0 twice using ram from the other board, and the symptoms don't change.
I've also tried the BIOS from the other board, another power supply, minimal config, and another EGA card, but it's always exactly the same!

Does anyone have any ideas on what it could be??

Thanks in advance for any replies.

Bobby.

modem7
October 29th, 2014, 12:22 AM
On the odd occasion it finishes post, at the point where it would boot from floppy, i get the error:
PARITY CHECK 1
00000 (S)
Looking at the source code for the 5170 POST/BIOS:

RAM parity error checking is enabled near the end of the POST. Some time after that, a parity error occured.
"PARITY CHECK 1" means that the error address is on the motherboard.
"PARITY CHECK 2" means that the error address is on an expansion card.

The "(S)" following the multi-digit number indicates two things:
1. A check for a "hot NMI" did not detect one.
2. Base RAM was searched in 64K blocks, and the segment portion of the error address printed to the screen followed by "(S)".

So the "00000" presented to you means that the error address is somewhere in the first 64K.


This tells me bank 0 is bad
Not necessarily. An analogy that I sometimes use is that of a 'low battery' warning light. If that light comes on, is the battery bad, or is the battery charging circuit bad, or is there some other electrical fault somewhere (draining the battery)?

In your case, one possibility is that your RAM is good, but there is a problem with the RAM refresh circuitry.


although I don't know what the S is for.
I am very sure that it is the BIOS indicating that the presented address is a segment one.


Time to try Supersoft/Landmark diagnostic ROMs.

bobba84
October 29th, 2014, 12:37 AM
Time to try Supersoft/Landmark diagnostic ROMs.

I'll give it a go. Thanks for your help! You sure know your stuff!

modem7
October 29th, 2014, 01:07 AM
You sure know your stuff!
On the IBM PC family, yes.
Put a Mac in front of me, and I will struggle - I don't even know any MAC-DOS commands.

bobba84
October 31st, 2014, 08:10 PM
Hi guys,

After modem7 kindly supplied me with some SuperSoft chips, I installed them and gave them a go.

First it did an error tone of 6 hi-lo followed by 1 lo, which according to the manual means unable to initialise video. Then 6 more hi-lo followed by 2 lo, which isn't documented.

Then, it started doing the tests. The results were the same each time, even when run 10 times in a row, and were as follows:

All passed except for CPU Protected mode. Is sat there for 10 seconds on this test, then it did the same beep codes as when it booted, then wrote FAILED over the text in the first row on the monitor, wrote PASSED next to the CPU protected mode test, added 1 to the error count in the bottom right corner, then continued. All other tests came back fine.

Here are a few screenshots:

21301

21302

21303

The supersoft manual recommended changing the CPU. So I pulled the CPU from the corroded board and tried again, but it gave the same results. I also tried two other video cards and nothing changed.

One thing to note - I do not have a CMOS battery installed. Could this cause a problem? I would have thought not, apart from not retaining CMOS settings... am I correct?

I am unsure how to proceed so any suggestions / advice would be greatly appreciated!

Thanks!
Bobby.

modem7
October 31st, 2014, 11:23 PM
First it did an error tone of 6 hi-lo followed by 1 lo, which according to the manual means unable to initialise video.
One of my clone CGA cards is a problem for the SuperSoft diagnostics. It does not cause SuperSoft to produce error tones, but instead, results in a corrupt display.
So maybe a subtle incompatibility between the diagnostics and your video card.
But of course, the error tones could be symptomatic of your motherboard problem.


All passed except for CPU Protected mode. Is sat there for 10 seconds on this test, then it did the same beep codes as when it booted, then wrote FAILED over the text in the first row on the monitor, wrote PASSED next to the CPU protected mode test, added 1 to the error count in the bottom right corner, then continued. All other tests came back fine.
I ran the SuperSoft diagnostics on my type 3 motherboard.
No CMOS battery, and the CMOS SETUP was in a blank state (motherboard had been in storage).

The PROTECTED MODE CPU test ran for almost exactly 20 seconds before displaying "PASSED" and then moving onto the next test.


The supersoft manual recommended changing the CPU. So I pulled the CPU from the corroded board and tried again, but it gave the same results.
Could you have been distracted and ended up putting the original CPU back in ?

bobba84
November 1st, 2014, 03:35 AM
Could you have been distracted and ended up putting the original CPU back in ?

I'm sure it was the other CPU. And I swapped it back too, with no change. I have since also tried again with another power supply, and with a genuine IBM CGA card. Still the same symptoms, same beep codes :(

The only thing I haven't done is remove the motherboard from the case and visually check for issues. I should have time tomorrow to do that.

mikey99
November 1st, 2014, 11:58 AM
Do you have the 6 Mhz or 8 Mhz version of the AT motherboard ? Does the crystal speed match the CPU speed X 2 ? 6 Mhz CPU uses a 12 Mhz crystal etc.
A popular speedup hack was to put a 16 Mhz crystal in a 6 Mhz board.....this worked most of the time :-)

BTW, just found this Sams for the 5170....good troubleshooting info :
https://archive.org/details/Sams-IBM-5170-with-type-1-motherboard

bobba84
November 4th, 2014, 12:06 PM
I have a type 1 board, and it has a 12MHz Crystal.

Thanks for the link! I'll have a good read and see what I come up with :)

bobba84
November 26th, 2014, 02:52 PM
I can't make sense of the contents of that link, sorry. I think it's a bit beyond my understanding.

Does anyone have any other ideas to try before I give up on this board? :(

Thanks...
Bobby.

3pcedev
November 29th, 2014, 01:18 PM
There is some physical "external" circuitry in the 5170 which allows the 80286 to return to real mode from protected mode. This is due to the fact that once the 80286 is in protected mode it cannot return to real mode without a 'reset'. I believe the circuit holds the contents of active memory while applying a reset.

It is possible that something is wrong here. I haven't read the 5170 technical manual to point you to exactly what hardware you need to look at; but perhaps someone here does?

EDIT: I just read that apparently IBM used the keyboard controller as a bit of a hack. As a bit of a last resort try swapping the KBC from your old motherboard onto this one. Also you are using an AT keyboard right? If you plug an XT one in it could produce some super weird error if the KBC is also handling protected mode/real mode reset. (Reference: http://www.rcollins.org/articles/pmbasics/tspec_a1_doc.html - have a look under exiting protected mode).

modem7
November 29th, 2014, 04:51 PM
There is some physical "external" circuitry in the 5170 which allows the 80286 to return to real mode from protected mode ...

I haven't read the 5170 technical manual to point you to exactly what hardware you need to look at; but perhaps someone here does? ...

EDIT: I just read that apparently IBM used the keyboard controller as a bit of a hack ...
A look at the circuit diagram of a type 1 motherboard indicates the following chip path for the type of reset that you are writing of:
U126 (keyboard controller) --> U105 --> U106 --> U94 --> CPU

Also involved are:
* U119 and U121 generate a dedicated SDCLOCK clock for U105
* U88 generates a SYSCLOCK clock signal of which U106 is one recipient

bobba84
November 30th, 2014, 02:10 PM
Thanks guys :)

The keyboard controller on this board isn't socketed, which it was on the first corroded board I had, which I find strange. I hope the keyboard I'm using is an AT one! I would have thought I couldn't press F1 to continue if it wasn't?

I'd better run home tonight and try the keyboard from my 486...

I don't have an oscilloscope or anything like that so apart from swapping out chips I don't know how much further diagnosis I can do... I could desolder and swap the Keyboard Controller chip from the corroded board and try it.

Bobby.

bobba84
December 9th, 2014, 12:58 PM
Hi guys,

After receiving another motherboard from modem7, I am glad and thankful to say that the 5170 is up and running!! :D

21773

All that is needed now is a CMOS battery, and for me to clean the floppy drive as it doesn't seem to read very well.

I just wanted to say thankyou to all involved in helping me get this system working!

Bobby.

cr1901
December 9th, 2014, 06:28 PM
Should you ever get your hands on another very sad AT, this video may provide some hints.

I just find repair videos relaxing in general, but this is relevant:


https://www.youtube.com/watch?v=5HXE84_piZg

jmetal88
December 9th, 2014, 06:57 PM
Should you ever get your hands on another very sad AT, this video may provide some hints.

I just find repair videos relaxing in general, but this is relevant:


https://www.youtube.com/watch?v=5HXE84_piZg

That's making me want to actually take a stab at repairing my original PCjr sometime. I was doing something with the lid open (can't remember what) and managed to accidentally short one of the power supply pins to something on the main PCB, instantly killing the machine. One of the nice guys on the PCjr forum felt bad for me and sent me a new machine for free, so I never got very far in trying to see which component(s) I actually killed. I still have the motherboard, case, floppy drive, and power supply stashed away somewhere.

bobba84
December 10th, 2014, 08:04 PM
Should you ever get your hands on another very sad AT, this video may provide some hints.

I just find repair videos relaxing in general, but this is relevant:


https://www.youtube.com/watch?v=5HXE84_piZg

Very cool!